(a) Field of the Invention
The present invention relates to an electron emission device, and more particularly, to an electron emission display device and a manufacturing method thereof in which the electron emission display device includes emitters made of a nano-size material, and gate electrodes for controlling electron emission.
(b) Description of the Related Art
In recent times, much research is being performed in the area of thick-layer processes, such as screen printing, to form electron emission regions. The electron emission regions are formed using a nano-size material that emits electrons at low voltage driving conditions of 10-100V.
Nano-size materials suitable for forming the emitters include Carbon Nano Tube (CNT) Graphite Nano Fiber (GNF), and Nano Wire. Among these, CNT appear to be very promising for use as emitters because they are able to emit electrons in low electric field conditions of about 1-10V/μm.
Examples of conventional electron emission devices utilizing carbon nanotubes and their manufacturing methods are disclosed in U.S. Pat. Nos. 6,359,383 and 6,436,221.
When the electron emission devices employ a triode structure of cathode electrodes, an anode electrode, and gate electrodes, they can have the type of well-known configuration shown in FIG. 5. With reference to FIG. 5, gate electrodes 3 are formed on rear substrate 1. Insulation layer 5 is formed on gate electrodes 3. Then cathode electrodes 7 are formed on insulation layer 5. Emitters 9 are formed on insulation layer 5 and cathode electrodes 7. Formed on front substrate 11 are anode electrode 13 and phosphor layers 15. Cathode electrodes 7 are formed of metal thin layer, for example, chrome (Cr) aluminum (Al) or molybdenum (Mo) with a thickness of 2,000-4,000 Å.
With the use of the above configuration, there is no possibility of short circuits occurring between gate electrodes 3 and cathode electrodes 7. Also, by forming emitters 9 on an uppermost layer of rear substrate 1, a thick-layer process such as screen printing may be easily performed. These factors make manufacture relatively simple, and are advantageous when producing large display devices.
However, cathode electrodes 7 made of the metal thin layer as described above have several problems. To begin with, when performing driving by applying a high voltage to anode electrode 13, arc discharges may occur in the display device. In this case, cathode electrodes 7 formed using the metal thin films may be damaged by such arc discharges. In addition, in large display devices, it is necessary that a resistance of cathode electrodes 7 be extremely small in order to realize moving images and multiple grays. However, there are limits to reducing the resistance of cathode electrodes 7 made of the metal thin films (they now have a resistance value of 3-5 Ω/□).
A conductive thick-layer material, which is not damaged by arc discharges and has a low resistance, has been considered as an alternative to metal thin films. However, fine patterning as when using metal thin films is not possible with conductive thick-layer material. Also, a thick-layer material limits the ability to increase resolution. Furthermore, since conductive thick-layer material is not resistant to acid, removal of a sacrificial layer (not shown) using an acid etchant damages the thick-layer material.
Therefore, when the cathode electrodes are formed using a metal thin layer, a method is typically used in which the cathode electrodes are more thickly formed to reduce resistance. However, a significant amount of time is required to perform this method and the remainder of the processes for forming the electrodes. Also, the problem of the electrodes becoming damaged remains.